(1) Field of the Invention
This invention relates, in general, to a new and improved fire extinguishing sprinkler head and, in particular, to a concealed, automatic fire sprinkler head suitable for use in residential dwellings. Even more particularly, this invention relates to a locking mechanism or keeper, for the valve assembly in a fire sprinkler head.
(2) Description of the Prior Art
Sprinkler systems are used extensively to provide automatic fire protection for residential, commercial and public buildings. Nevertheless, for a sprinkler head to qualify as suitable for use in a residential sprinkler system, the sprinkler head must pass many tests, several of which go beyond those normally used for ordinarily commercial/industrial type sprinkler heads. The two greatest distinctions between ordinary and residential type sprinkler heads are the operating speed and specially designed water spray patterns that fire tests have revealed are necessary to combat or extinguish a fire in typical residences. The residential type fire sprinkler head must operate at a faster speed than the ordinary commerical/industrial sprinkler head, the faster the better, as the protection of human life is involved. Thus, there is a keen interest in providing residential sprinkler heads with even shorter times to become operable.
The primary purpose of a fire sprinkler system is to extinguish or, at least, contain a fire prior to the arrival of fire fighters and fire fighting apparatus. The theory behind the use of fire sprinkler systems is that, by preventing a fire from getting out of control, property damage is minimized and, even more importantly, in the case of residential sprinklers, lives can be saved.
At one time, the greatest danger from a fire in the home was being trapped by flames and burned or suffocated by smoke. However, in more recent years, residential dwelling are being furnished with, or contain furnishings and fixtures which, because they are made of, or contain synthetic materials, give off highly toxic fumes when ignited or heated to a sufficient degree. Thus, it has become increasely clear that many fire fatalities result from inhaling toxic fumes produced by the fire rather than from the fire itself or smoke produced thereby.
In many cases, fire victims are overcome by these toxic fumes and die in their sleep long before the fire becomes intense enough to be noticed by inhabitants of the dwelling or by neighbors. The recognition of this problem has lead to the extensive use of heat and smoke alarms for alerting inhabitants of a dwelling that a fire is in progress. The early alert which is provided by these alarm systems enables the inhabitants to leave the dwelling while it is still safe to do so.
The use of smoke and heat detectors, however, does not diminish the importance of a fire sprinkler system. Although individual safety is of prime importance, the loss of one's home and worldly possessions, represents a tragic event. Also, a fire which is out of control represents, in some cases, a potential threat in spreading to adjacent property, thereby endangering the lives of other individuals. A fire out of control also represents a danger to fire fighters and to individuals who may not be able to leave the residential dwelling quickly, or perhaps not even at all, such as might be the case with small children, infants, the ill, handicapped persons, or elderly residents of a nursing home.
An automatic fire sprinkler head, whether of the commercial/industrial type or one for residential dwellings comprises, in general, an elongated tubular-shaped body member which is open at one end, and is connected to a fire extinguishing fluid, e.g., water, line. The other end of the body member is ordinarily maintained closed by a valve assembly which is locked in that closed position by a locking mechanism or means comprising, in part, a heat fusible alloy composition of low melting point, until the onset of a fire. When a fire occurs, and the ambient temperture reaches some predetermined level, corresponding to the melting point of the alloy composition used, the alloy melts, resulting in the inactivation of the locking mechanism and freeing the valve assembly to move to its open position whereby the fire extinguishing liquid is then discharged from the fire sprinkler head.
Over the years, various locking means have been used, to maintain the valve assembly in a fire sprinkler head, in the closed position. Exemplary of this prior art are U.S. Pat. Nos. 4,015,665; 4,491,182; and 4,508,175.
As disclosed in U.S. Pat. No. 4,015,665, the outlet of the sprinkler head orifice body disclosed therein is normally closed by a valve cap and the valve cap is held in that closed position, until the onset of a fire, by what is termed a "latch assembly", which assembly includes a so-called "latch bar". The latch bar, in one embodiment of the invention as shown in FIG. 1 in that patent, is an elongated, horizontally disposed member which at one end is forked and is provided with a pair of projections. These projections engage an annular lip or abutment which borders the lower edge of a circumferential groove formed in the downwardly extending flange of the orifice body. The other end of the latch bar is provided with a bore or recess in which is located a slug of a low melting point, fusible alloy. At the outer end of the slug, there is formed a depression for a ball, which projects outwardly from and beyond the end of the latch bar. Thus, the ball is engaged with the annular lip or abutment, at a location directly opposite from that engaged by the projections at the other end of the latch bar. When a fire occurs, and the ambient temperature rises to the point where the fusible alloy melts, the ball is caused to move inwardly of the recess, thereby snapping over the edge of the lip or abutment, to release the latch bar.
In a further embodiment, shown in FIG. 5 in U.S. Pat. No. 4,015,665, the latch bar is of a modified construction wherein the recess communicates with a downwardly extending threaded opening. A housing containing a fusible alloy is threaded within the opening whereby, in combination with the bore, there is defined an L-shaped passage. Three balls are located within the passage whereby the inner ball is located partially within a depression in the fusible alloy and the outer ball is engaged with the annular lip or abutment formed in the flange on the orifice body. The engagement of the outer ball with the abutment can be made tight by threading the housing upwardly in the threaded opening of the bore. The housing containing the fusible alloy, being directly exposed to any fire, according to the patentee, results in a faster rate of response than where the fusible element is located well above the ceiling, behind a decorative plate.
In both U.S. Pat. Nos. 4,491,182 and 4,508,175, the outlet end of the orifice body is maintained closed, until the onset of the fire, by an assembly which includes a valve plug kept in position by directly opposed locking balls, which engage a groove located within the outlet end of the orifice body. The locking balls, in both cases, are forced outwardly against the groove and are kept in that position by the tapered surface of an elongated plunger, which is capable of vertical up and down movement. The elongated plunger is located within a housing which can be threaded upwardly to cause the balls to move upwardly and outwardly against the orifice body groove. Within the housing, at the bottom, is located a heat fusible alloy disc which, in turn, supports the elongated plunger. Upon melting of the heat fusible alloy disc, the plunger drops, allowing the locking balls to move inwardly from the groove, and the valve plug to move vertical downwardly, freeing the outlet end of the orifice body for discharge of fire extinguishing liquid.
Although various fire sprinkler heads invented heretofore have been found satisfactory to a degree, there still remains the quest for ever more sensitive and rapid responding sprinkler heads. Moreover, there is a continual desire that sprinkler heads be provided that not only are capable of fast response, in the event of a fire, but that are of economical construction and simple in operation and design.